I was driving with my friend as well, breaking no traffic laws when he got pulled over and ticketed for an exhaust in his GSX eclipse. So, yes you can get a ticket for that. Also, that ticket WILL put 2 points on your lisence (in Mass), and raise insurance premiums.
Also, I believe visiondynamix is correct, both a catted DP and catless DP are equally illegal. If I remember correctly it is a federal fine to remove and/or replace a functioning catalytic converter. Also, unless the cat in those is a "3 bed" that can remove NOx as well, it would be illegal.
Also, with any DP, it is very strongly recomended you get a tune, catted or catless. Which also getting a tune and modifying the OBD functions on the ROM is also illegal.
Moral of the story is no matter what you do away from stock is illegal.